Mobile devices are becoming prolific and growth exponential. The market in western countries is saturated with mobile devices, but developing countries present great growth potential. What is more, western countries present growth opportunities for more advanced smart phones, which are becoming integrated into people's lives. Many developing countries use written languages with a large number of characters relative to the English Alphabet. Therefore, having independent keys for each character is difficult or impossible to implement on a device with a small form-factor.
Input devices for mobile communication devices have typically included at least a standard numeric keypad typical of well-known telephones. As mobile devices become more advanced, more sophisticated input devices can be used to improve input efficiency. For example, modern cellular devices can include QWERTY keypads, speech-to-text, touch screens, trackballs, optical trackpad assemblies and other input devices that allow a user to enter data.
An optical trackpad assembly typically includes an optical trackpad that can be positioned on the front surface of a handset, just below the display. An infrared light source located below the trackpad can emit infrared light towards the trackpad, and when a user places a finger on the trackpad, a sensor can detect the finger. The sensor can detect the user's finger by receiving infrared light that can be reflected off the user's finger. The handset can also determine the direction of motion of the user's finger on the trackpad, and the finger's motion can be translated into corresponding functions associated with the handset.